Research: Ultrafast Rotation of Molecules with X-rays

2019-02-08

Uppsala scientists have in an international cooperation studied how fast the carbon monoxide molecule rotates when it is irradiated with x-rays. The research was published in the reputed scientific journal PNAS on February 7, 2019.

Ultrafast rotation of the CO molecule due to recoil by emission of an energetic photoelectron. Wk is the angular velocity, and the time t varies between 0 and the core-hole lifetime (7 femtoseconds). Image: Maria Novella Piancastelli.

Maria Novella Piancastelli and Hans Ågren, at the Department of Physics and Astronomy at Uppsala University, have carried out an experiment based on the photoelectric effect, which Albert Einstein received the Nobel prize in physics for in 1921.

By irradiating carbon monoxide molecules with x-rays, the researchers have created a chain reaction where very energetic electrons are emitted from the carbon atom. Because of this released energy, the molecule left behind feels a “push” which leads to rotational motion. The rotation of the molecule happens really fast, on the timescale of a few femtoseconds (10-15 s). By adjusting the energy of the x-rays, the scientists have also been able to affect how fast the carbon monoxide molecule rotates: the more energy, the faster rotation.

This type of manipulation, to be able to rotate molecules at very high speed with the help of light, produces a new possibility to affect motions at microscopic level and has great significance for various applications within natural science, including for example in optical micro machines. The construction and control of molecular machines is a sought-after goal in chemistry and biology, with numerous applications in medicine and life sciences.

“This research gives us exciting new possibilities of inducing and controlling mechanical movements on a microscopic, even molecular, scale”, says Maria Novella Piancastelli, professor at the Department of Physics and Astronomy.

Article Reference

D. Céolin, J.-C. Liu, V. Vaz da Cruz, H. Ågren, L. Journel, R. Guillemin, T. Marchenko, R. K. Kushawaha, M. N. Piancastelli, R. Püttner, M. Simon, and F. Gel’mukhanov, Recoil-induced ultrafast molecular rotation probed by dynamical rotational Doppler effect, PNAS (Proceedings of the National Academy of Science of the United States of America) February 7, 2019

Camilla Thulin